In a semiconductor manufacturing apparatus, a product yield is greatly affected by adhesion of particles to a substrate during a manufacturing process. To this end, the substrate is cleaned before or after the processing. However, it is required to develop a cleaning technique for simply and reliably removing particles while reducing damage to the substrate. As for a cleaning technique that is being currently studied and developed, there is suggested a technique for peeling off particles from a surface of a substrate by applying physical shearing force greater than adhesive force between the particles and the substrate. A technique using physical shearing force of a gas cluster is an example thereof.
The gas cluster is an aggregate of atoms or molecules obtained by ejecting a high-pressure gas in vacuum and cooling the gas to a condensation temperature by adiabatic expansion. During the cleaning of the substrate, particles are removed by irradiating to the substrate gas cluster with proper acceleration or no acceleration. The gas clusters are obliquely irradiated to the substrate. Therefore, in the case of removing the particles adhered to the pattern on the surface of the substrate, the pattern acts as a structure in view of the particles. Accordingly, it is difficult for the gas cluster disturbed by the structure to reach the particles, and this makes the removal of the particles in the recess difficult.
Further, the present inventors have discovered that the particle removal rate may vary even in the case of using the same gas cluster nozzle and the difference in the removal rate is related to diameters of the particles. When the particle removal rate is low, an acceleration voltage of gas clusters may be increased to increase kinetic energy. In that case, however, the surface of the substrate may be damaged.
In Japanese Patent Application Publication No. H4-155825, there is illustrated a drawing showing that clusters of a rare gas are perpendicularly incident on an object surface. However, a difference in a removal rate in accordance with diameters of particles is not described.
In addition, Japanese Patent Application Publication No. H11-330033 discloses a desired size of clusters for the case of removing micron particles or sub-micron particles. However, the object of the present invention and the solution thereto are not disclosed therein.